check for non-ascii characters in docs

[GernotMaier]

Deployment of github pages fails with non-ascii characters in the rst files (see #669)

Add a workflow step to check RST files and exit if there are non-ascii characters.

[codecov]

Codecov Report

Merging #671 (1fa15a6) into main (afaa144) will not change coverage.
Report is 1 commits behind head on main.
The diff coverage is n/a.

@@           Coverage Diff           @@
##             main     #671   +/-   ##
=======================================
  Coverage   99.29%   99.29%           
=======================================
  Files          39       39           
  Lines        3551     3551           
=======================================
  Hits         3526     3526           
  Misses         25       25           

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[VictorBarbosaMartins]

Hi Gernot. As I do not know where to check to see whether the workflow is working, could you please provide more information in the PR?

[GernotMaier]

See the test here: https://github.com/gammasim/simtools/actions/runs/6823947507/job/18558879126

I have put non-ascii characters into one rst file and the code works as expected.

[VictorBarbosaMartins]

Ok, thanks! then this is very good.